The technical scope of the invention is that of igniter tubes, notably for artillery.
Known igniter tubes generally incorporate a stack of tablets of igniting composition, for example black powder, placed inside a tube, generally metallic.
Today, ammunition used in combat vehicles more and more frequently comprises a case made of a combustible material.
Thus, after the ammunition has been fired, the only part to be ejected from the chamber and then temporarily stored in the turret is the metallic base.
Metallic igniter tubes have the disadvantage of protruding from the base thereby complicating its ejection and storage.
Patent FR-A-2593905 proposes the replacement of the metallic tube by a heat-shrinkable sheath that keeps the tablets together as well as a case carrying igniting means (for example a squib), such case being attached to the base by screwing.
The advantage of such a solution lies in that it ensures the quasi-total combustion of the igniter tube. The only incombustible part is formed by the support case that is of a height that is less than that of the base and thus does not hinder its ejection.
Moreover, the tube has a certain flexibility that facilitates its installation in the load.
However, this tube still has certain drawbacks.
The heat-shrinkable sheath has thus been found to be subject to embrittlement along the joins between the tablets and the support case. Such embrittlement can lead to fracture further to the mechanical vibrations and stresses to which the ammunition is subjected during the transport and storage phases.
Such an embrittlement is due partly to the grains of powder striking the joins between the stack of tablets and the support case, and partly to the stresses that are developed within this join during bending movements of the igniter tube.
The aim of the invention is to propose an igniter tube that overcomes such drawbacks.
Thus, the igniter tube according to the invention retains the flexibility conferred by the heat-shrinkable sheath but provides improved stress-resistance.
The tube according to the invention is simple in design and can be produced at a reduced cost.
Thus, the invention relates to an igniter tube, notably for artillery ammunition, and comprising a stack of at least two ring-shaped tablets made of an igniting composition and joined together by a heat-shrinkable sheath and ignition means for these tablets that is integral with a case, wherein the case incorporates a tubular part inside which the stack of tablets is introduced leaving a little play, the tubular part thus covering at least part of the stack, and wherein it comprises a ring made integral with the tablets by the heat-shrinkable sheath, said ring incorporating an abutment surface that is held by retention means against a matching surface carried by a bore of the case.
According to a preferred embodiment of the invention, the bore arranged in the tubular part is conical in shape, the tip of the cone being on the ring side.
The ring will preferably be made of a compressible material.
The compressible material can be selected from among the following materials: polyurethane elastomer, rubber, nitryl, polyurethane foam.
The abutment surface of the ring can be a conical surface.
The retention means can be formed by a plug integral with the case and supporting the ignition means.
The tubular part will preferably be of a length able to cover five tablets.
The tubular part is provided with at least two radial holes evenly spaced angularly.